Lubricating oil thickened with a metal soap of an alpha sulfo-fatty acid



2,951,809 rnromunn WITH A METAL SOAP or AN ALPHA SULFO-FATTY ACID John Nelson, Lansing, lll., assignor to Sinclair Refining Company, New York, N.Y., acorporation of Maine w No Drawing; FiledMar. 1, 1955, Set. No. 491,540

3 Claims. 01.252 33) droppin point greases in particular, is the soap empi'dyeuas the thickener. Consequently, these in the art areednstanuy insea'rch of means for reducing the amount ap ifiequired in a grease of a given penetration, ing tor alternate fatty substances which may be in r supply or otherwise less expensive and attempting to ub'stitiite less expensive saponitying components for these presently used. These considerations are especially acute with the so-called premium greases such as those containing lithium l 2-hyd'roiiy stearate. The fatty component in such premium greases is, generally, hydrogenated castor oil or 12-hydroxy stearic acid, and continued and increased uses of these greases have made the search for substitutes forthe fatty components and the lithium nec l in casive One of the characteristics which classifies a grease as a premium grease is a high dropping point; thus, a lithium l2-hydrox'y steara'te grease willhave a dropping point in the range-of above about 400 F. andanhydrous calcium l2-hydroxy s'tearate grease drops at about 300 F.

while ordinary calcium stearate cup greases have low tlropping points on the order of 220 F. The present invention is particularly related to grease compositions evidencing high dropping points.

I have now discovered novel grease compositions which are characterized by high dropping points. These high dropping point grease compositions in general comprise a lubricating oil thickened to grease consistency with a soap of an alpha sulfo fatty acid, preferably a saturated fatty acid, having. 12 to 22 carbon atoms per molecule.

Grease compositions within the scope of the present invention'includ'e as the thickening component soaps of alpha-sulfo faty acids. These sulfo-fatty acids include, to:"example,'alpha sulfmmyristic acid, alpha-snlfo stearic acid and alpha-sulfo-palmitic acids. Mixtures of the various acids Within the class can also be used. Particularly desirable greases result when the fatty component employed is alpha-sulfo-stearic acid, alpha-sulfo palm itic acid, or a mixture of the alpha-sulfo stearic and pah nitic acids.

The fatty material can be saponified to produce the soaps employed in my invention. In general, alkali metals and alkaline earth metals constitute the main groups of metals which can be used. Particular componentsinclude, for example, sodium, calcium, lithium, potassium, magnesium, strontium, barium and mixtures of the foregoing, with calcium, lithium and mixturesof sodium and calcium being especially desirable. Saponifying components are used in any of the usual forms, for

example, as hydroxides, oxides, carbonates and the like.

The resulting soaps generally constitute about 5 to '25 Weight percent of the compositions and preferably about 10 to 20 percent.

Mineral oils or synthetic oils which normally are used in preparing grease compositions can be used in the present invention. The mineral oil fraction can be obtained from Mid-Continent, paraffinic and naphthenic crudes. In general, it is preferred that a mineral lubricating oil fraction having a viscosity within the range of about 50 SUS at F. to 1500 SUS at 210 F. be employed. The'oil traction can be highly refined and solvent treated, if desired, by known means. Among the'synthetic lubricants which can be used are polymerized olefins, alkyl'ated aromatics, silicone polymers, polyalkylene glycols and their partial or complete ethers and esters. Also I can use synthetic lubricants such as diesters of dibasic acids, e.g. di(2-e thyl hexyl) adipate and di(isooctyl) azelate, and the like.

Grease compositions of the present invention are prepared by thickeningthe oil fraction with soap of an alpha-'sulfo fatty acid of the class described. The soaps employed can be preformed, or they can be prepared in situ. When a mono-v alent saponifying component is employed, soap formation can be effected. by any of the procedures known to the art. For example, both low and high temperature saponification procedures are eifective as are saponification in part of or all of the oil of the final composition. On the other hand, saponification of the fatty component with a divalent material introduces a measure of flexibility permitting difierent soaps tobe produced. Thus considering the following formula H where R is an alkyl group for instance having 12 to 20 carbon atoms it can be observed that a divalent metal canetlect joinder of a plurality of molecules of the acid in a variety of ways. Examples include the following where M is a divalent metal:

The two functional groups of a single molecule also can be. joined as follows:

Other soaps which can be produced include polymeric a monovalent metal or esterifying such remaining acid groups, particularly with a lower alkyl alcohol.

The various embodiments may be obtained through use of conventional blocking procedures, since the two acid groups present are of such diverse strength. Preferred calcium greases are produced by employing about 1.50 to 2.50 moles of calcium per mole of fatty component and adding the calcium incrementally, for example adding about half of the calcium slurried in starting oil, to a mixture of the acid and Water and then adding the remainder of calcium after reaction has been initiated. The soap resulting appears to have the structure indicated under III above.

Premium grease compositions characteristically are substantially anhydrous, i.e., the finished greases have a Water content below about 0.10 weight percent and preferably below about 0.05 weight percent. Grease'compositions of the instant invention also are substantially anhydrous. Dehydration to result in this state can be accomplished in any manner but preferably by maintaining the temperature of the reaction mass, after completion of saponification, at a temperature above the boiling point of water for about 2 to 4 hours. While dehydration can be affected after finishing oil has been added, it is preferred to dehydrate prior to the addition of finishing oil in order that less material need be handled.

Grease compositions of the present invention can be formulated with a plurality of soaps. The use of a soap of an alpha-sulfo fatty acid, as noted before, results in a grease composition characterized by a high dropping point. This advantageous property can be obtained in a grease composition without the necessity of employing the alpha-sulfo soap to the exclusion of other soaps. For example, grease compositions can be made employing calcium 12-hydroxy stearate and calcium alpha-sulfo stearate with the result that a higher dropping point will be evidenced than would be evidenced by the grease containing only calcium 12-hydroxy stearate. Plural soap greases of this nature are additionally advantageous in that the stabilizing agents normally employed as in calcium containing greases need not be employed since calcium soaps of alpha-sulfo-saturated fatty acids unexpectedly exert a stabilizing efiect on compositions of which they form a part. Where soaps of alpha-sulfa saturated fatty acids are employed in conjunction with other soaps, the former generally constitutes about 5 to 75 weight percent of the total soap content.

Materials normally incorporated in greases to impart special characteristics can be added to my compositions. These include oxidation inhibitors, corrosion inhibitors, extreme pressure agents and anti-wear agents. The amount of additives added to the grease compositions usually ranges from about 0.01 Weight percent up to about 10 weight percent and, in general, can be employed in any amounts desired so long as the present invention is not deleteriously aifected.

The invention will be described further in conjunction with the following specific examples. It should be understood that the invention is not to be limited by the details disclosed in the examples.

EXAMPLE I An anhydrous calcium grease was prepared as follows: 195 grams of alpha-sulfo stearic acid were treated with 22 grams of lime slurried in 400 grams of conventionally refined naphtenic type oil, having a viscosity of 200 SUS at F. and 195 grams of water. This mixture was stirred in a jacketed grease kettle at room temperature for 15 minutes. Steam was gradually introduced into the jacket until the kettle contents were heated to F. Then an additional 25 grams of lime slurried in 400 grams of the oil were added to the kettle and the temperature was slowly raised to 250 F. The temperature was held at about 250 F. for 2 /2 hours to insure essentiallycomplete dehydration and to form the desired soap grease structure. One percent of Age-Rite Resin D-oxidation inhibitor (trimethyldihydroquinaline polymer marketed by B. F. Goodrich) was then'added, finishing oil was added amounting to about 700 grams of oil and the grease was stirred until it cooled to 200 F.

Tests on the grease are as follows:

. Table I Penetration data: A Unworked 306 Worked, 60 strokes 352 Dropping point, F. {374 EXAMPLE II i In the preparation of a lithium alpha-sulfo'stearate grease, 51 got lithium hydroxide mono-hydrate dissolved in 250 grams of boiling water were added to 198 grams of alpha-sulfo stearic acid dispersed in 600 grams of a conventionally refined napthenic oil, having a viscosity of 750 SUS at 100 F. at 200 F. The temperature was raised to 338 F. during dehydration. One percent-Iof Age-Rite Resin D oxidation inhibitor was added in con junction with finishing oil in the usual manner, while the grease cooled. to about 200 F. The grease was milled-at .005 clearance in a conventional colloid mill.

Tests on this grease indicated:

From the above examples it is readily apparent that greases of my invention are characterized by veryhigh dropping points.

What is claimed is: i y

l. A grease composition consisting essentially ofa lubri cating oil base thickened with a soap of a fatty acid'hav ing twelve to twenty-two carbon atoms per molecule and a SO H radical attached to the alpha carbon atom and a metal selected from the group consistingof metals and alkaline earth metals. i

2. The grease composition of claim 1 soap is a calcium soap;

3. The'grease composition of soap is a lithium soap.

which said claim f wa e 5 6 References Cited in the file of this patent OTHER REFERENCES UNITED STATES PATENTS Recueil des Travaux Chimiques Des Pay-Bas, v01. 18,

, pp. 211-214, 1899. SEE 2:; et a1 "32? 5 Chemical Technology and Analysis of Oils, Fats, and 2666744 Dixon 1954 Waxes, Lewkowitsch, fifth ed., v01. 1, Macmillan C0.,

N. Y., 1913, pp. 145 and 146.

FORE GN PATENTS Evidence for Alpha Sulfonation in the Reaction of 288 612 Great Britain p 21 1928 Pahnitic Acid With Sulfur Trioxide, J. K. Well at al., 607:204 Great Britain Aug. 28, 194:; JACS 2526 (1953)- 

1. A GREASE COMPOSITION CONSISTING ESSENTIALLY OF A LUBRICATING OIL BASE THICKENED WITH A SOAP OF A FATTY ACID HAVING TWELVE TO TWENTY-TWO CARBON ATOMS PER MOLECULE AND A-SO3H RADICAL ATTACHED TO THE ALPHA CARBON ATOM AND A METAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METALS AND ALKALINE EARTH METALS. 